Add UX Manager as a new core maintainer role

I didn't expect the significant changes here to the Product manager role. Not yet sure if I agree or disagree with all those changes.

Is a 'Needs UX manager review' tag needed?

Collaborating with product and framework managers to ensure UX solutions are feasible, scalable, and aligned with strategic priorities

@quietone @catch with your feedback basically I would have listed everyone, so let's just say Leadership team as for the Product manager?

I didn't expect the significant changes here to the Product manager role.

Both @lauriii @gábor hojtsy and @dries reviewed and agreed with this changes. The way the Product manager role was explained wasn't reflecting what a Product manager usually does, plus incorporated all user-facing responsibilities that belong to UX. Since I muved all the user-facing tasks and responsibilities under the UX manager (and explained them) I added what is expected from a Product manager nowadays. Is there any specific feedback I could address?

Is a 'Needs UX manager review' tag needed?

We do have "Needs usability review" and that's just a small part of UX. UX means the whole user experience or also design and UI. One thing is make sure that something is usable, the other is getting a +1 of someone that has in mind the user flows for the task and can get a holistic overview, which would be the UX manager and not a normal contributor that might lack the whole context. They are 2 different responsibilities/kind of reviews.